This invention relates to the field of multi layer capacitors. More particularly, this invention relates to a multi layer capacitor which incorporates a flexible high dielectric constant sheet material as its insulator which results in a high capacitance, low inductance capacitor.
It will be appreciated that there is an ever increasing need for a reliable, flexible high dielectric material which may be used for a variety of applications in electronic circuitry design and manufacture. Presently, flexible high dielectric materials of this type are manufactured by mixing small particles (e.g. 1-3 microns) of a high dielectric constant material into a flexible polymeric matrix. Surprisingly, the resultant effective dielectric constant of the dielectric impregnated polymer is relatively low. For example, the dielectric constant of a Z5U BaTiO.sub.3 is in the range of 10,000 to 12,000. However, when such Barium Titanate is mixed with a flexible polymer such as polyimide, polyester, polyetherimide and like materials, the effective dielectric constant realizable is only on the order of 20 to 40 (depending on the loading ratio of the dielectric in the polymer).
It will be further appreciated that a need exists for a very high capacitance capacitor that has low inductance and low equivalent series resistance (ESR). This need is especially perceived in applications such as noise suppression in high current power distribution systems for digital computers, telecommunications modules, AC ripple filtering in DC power supplies, etc.
It will be appreciated that prior art capacitive devices all suffer from high ESR and high expense. An example of a prior art device is an aluminium electrolytic capacitor which has a high ESR (Equivalent Series Resistance), is bulky and is awkward to install. Another example of a prior art device is a large monolithic ceramic capacitor which is very expensive. Yet another example of a prior art device is a Tantalum capacitor which has a high ESR and is only suitable for very low voltages of three to six volts.